In a process for manufacturing a semiconductor device such as an LSI or a VLSI, a liquid crystal display panel, and/or the like, patterning is performed by exposing light onto a photosensitive layer or the like via a mask (also referred to as an exposure negative or a reticle). When there are foreign particles attached to the mask upon patterning, the light is absorbed or bent by the foreign particles. As a result, the formed pattern is deformed, the edges are rough, and there is a loss in the dimensions, the quality, and the appearance of the patterning, and the like. In order to solve such a problem, a pellicle is used which is a dustproof cover including a pellicle membrane that allows light to pass through onto a surface of a mask, in order to prevent the attachment of foreign particles to the surface of the mask.
A pellicle generally includes a metal pellicle frame and a pellicle membrane disposed on one end surface of the pellicle frame. A mask adhesive layer for fixing the pellicle to a mask is formed on the other end surface of the pellicle frame. A sheet-shaped material (separator) that has releasability in order to protect the mask adhesive layer is normally disposed on the surface of the mask adhesive layer.
For mounting the pellicle on the mask, the separator is peeled so as to expose a mask adhesive layer, and the pellicle is pressure-bonded and fixed at a predetermined position of the mask via the exposed mask adhesive layer. By mounting the pellicle on the mask in this manner, the mask can be irradiated with light while the influence of foreign particles is eliminated.
As an adhesive used for a pellicle adhering to a mask, an adhesive is proposed that contains a hydrogenation product of a block copolymer having a saturated cyclic hydrocarbon structure, such as a styrene/isoprene/styrene triblock copolymer, and a tackifier (see, e.g., Patent Literature 1). In addition, a hot melt adhesive containing a styrene/ethylene/propylene/styrene triblock copolymer and an aliphatic petroleum resin is proposed (see, e.g., Patent Literature 2). A pressure-sensitive adhesive containing two types of block copolymers having a polymer block composed of an alkyl (meth)acrylate ester, and a tackifying resin, such as a (hydrogenated) petroleum resin, is also proposed (see, e.g., Patent Literature 3).
In order to highly integrate semiconductor devices, it is necessary to make a formed pattern finer. In other words, in order to integrate many semiconductor devices in a narrow area, it is necessary to decrease the size of semiconductor devices as much as possible. Therefore, it is necessary to decrease the width of a circuit pattern, and the spacing (pitch) between adjacent circuit patterns. However, there is a resolution limit to a pattern forming method using photolithography, and therefore, there is a limit to making a pattern finer.
As a method for overcoming such a resolution limit in the photolithography process, double patterning is known. Double patterning is a technique where one circuit pattern is split into two parts, and exposure is performed for each split pattern to ultimately obtain a high-density fine pattern (see, e.g., Patent Literatures 4 and 5). Double patterning is preferably applied to the manufacture of semiconductors of 22 nm node (half pitch: 32 nm) and beyond.
In double patterning, exposure is normally performed twice using two masks. Therefore, it is important for double patterning to increase a precision of the relative positions of two formed patterns. In other words, when the precision of the relative positions of a pattern obtained by the first exposure and a pattern obtained by the second exposure is low, the desired pattern cannot be obtained. Therefore, it is necessary to decrease an amount of the pattern displacement between the formed circuit pattern with the two masks and a designed circuit pattern to the nanometer (nm) level.